This invention relates to methods and apparatus for rolling rolled materials widthwise thereof, and more particularly it is concerned with a method and apparatus of the type described capable of avoiding, when a slab of metal having a large width as contrasted with the thickness is rolled widthwise thereof, formation of fishtails at the lengthwise ends of the slab.
Generally, a rolled material produced by continuous casting or rolling of an ingot has its width reduced in the next operation step by means of a widthwise rolling mill having vertical rolls, so that the rolled material will have a predetermined width. When widthwise rolling of the rolled material is carried out, difficulties have been encountered in causing the rolling operation to have effects in the interior of the rolled material and elongation has tended to occur only on the surface layers thereof. As a result, the rolled material has a recess at either end thereof. The recess is referred to as a fishtail and its amount is represented by its maximum depth. The fishtail should be discarded because it is not suitable for use in industrial production, thereby causing a reduction in the yield of the rolled material.
Heretofore, it has been usual practice to regulate a pass schedule to minimize the fishtail in view of the fact that the amount of the fishtail varies depending on the pressure applied to the rolled material widthwise thereof by the rolls. Japanese Patent Publication No. 16786/78 discloses one example of the prior art. The process for avoiding formation of a fishtail has, however, been unable to achieve a success in avoiding formation of fishtails. Moreover, the process has been found to have the disadvantage that the rolled material is difficultly bitten by the rolls.